Improving Kato UniTrack HO Points for DCC Operation

Kato UniTrack is a very good product and allows reliable trackwork to be assembled quickly without the need to cut and solder track.  Most Kato turnouts, including N scale, have the ability to be switched between power routing and non-power routing, but the No.4 HO turnout, as pictured below, doesn’t. So in this week’s post I’ll show you how I modify Kato UniTrack No.4 turnouts for use with DCC.

But what does power routing mean?  Below is an extract from showing how the turnout isolates different routes depending on how it’s set.

For DC operation, power routing is very useful as power is delivered only where you want the train to run.  The other route is isolated so any trains on that line won’t move.  However for DCC all the tracks want to be powered so the turnout ideally wants to be non-power routing.  As I said earlier most Kato turnouts can be switched between power routing and non-power routing but the HO No.4 can’t.

In the No.4 box you get the actual turnout and associated track parts.

The actual turnout has an all metal frog shown in green, electrically linked blades shown in yellow and switched rails shown in blue.  The stock rails are marked red and black; these have the incoming power.

Between the frog and the switched rails is a plastic insulator.  It’s these two rails which ideally need to be electrically connected permanently for DCC operation.  However the frog changes polarity depending on how the turnout is set so you simply can’t solder the switched rails to the frog.

On the underside of the turnout are five screws holding on the base plate.

Under the base plate you can see the electronic switch and the solenoid which changes the turnout.  In the image below the turnout is set for the straight route. The ‘T’ section in the center of the switch is connected directly to the frog and bridges power from the right side to the left.  This connects the frog and the relevant exit rail or switched rail back to the black stock rail.

In the image below the turnout is set to the diverging route and the ‘T’ section connects the switched rail and frog back to the red stock rail.

To make the turnout non-power routing is a fairly simple fix.  I use two short sections of wire, as shown below.

These two wires are soldered to the copper plates as shown below.  The upper wire links the red stock rail to the diverging switched rail.  The lower wire links the black stock rail to the straight switched rail.

And that’s it.  This modification also makes the turnout even more reliable as the power is transferred through the new wires rather than the contacts in the ‘T’ sections.

With the base plate replaced the turnout is ready for use on a DCC layout.  It can still be used on a DC layout, the turnout simply won’t act as a power router. Also, if you’re not into soldering, this modification can be done away from your layout at a model club or possibly a local hobby store as the Kato turnouts will remain self-contained.

How to Fix Runaway Locomotives on a DCC Layout

When running your layout on DCC power have you ever had the problem of trains suddenly rocketing off down the track at full speed for no apparent reason?  Well a fellow modeler had just this problem this weekend.  So in this post I will explain what was causing his issue and what you can do to avoid it.

Before I can say why there’s a problem I need to explain a bit about how DCC works.  DCC powered trains all have a decoder inside which receives power and instructions through the track.  This combined supply is a 12V to 16V AC (Alternating Current) signal.  The decoder splits this into two separate parts.  The first part is the AC power which runs through a bridge rectifier.  This converts the AC power into 10V to 12V DC (Direct Current).  The DC is used to power the decoder and any outputs, such the motor and lights.  The second part takes the instructions, which are carried in the AC Bi-polar Square Wave as packets, and feeds them into the decoder processor.

(A Bi-polar Square Wave is not the same as a Sine Wave which you may have seen on an Oscilloscope screen trace; one is a series of square shaped variable width pulses and the other is smooth curved [Sinusoidal] and has a constant period time-base. The DCC signal as well as being square in shape has a variable time-base. By varying the width of each square wave pulse, a digital binary data bit can be transmitted. A binary 1 or a binary 0. It is the pattern of ones & zeros that define the DCC command being sent.).

The instructions will be things like increase speed or turn on light.  The DCC command station sends out many packets every second, that’s why the decoder can do many things at once.

A lot of decoders have the ability to run on traditional DC powered (Analog) layouts as well as DCC.  This is achieved by the processor understanding what type of power it’s receiving.  For example, if a locomotive with a suitable DCC decoder is put on a DC layout there will be no power applied until the DC throttle is turned on.  As the processor starts to receive a DC power supply but no information packets it realizes it’s on a DC controlled layout; this takes barely a second.  So it bypasses all of its complicated circuits and sends any DC power received directly to the motor and lights.  This makes the locomotive behave just like a normal DC locomotive.  It repeats this every time it’s moved on a DC layout.

The next time the locomotive is put on a DCC layout the second it receives an information packet it knows it’s on a DCC supply and returns to normal.

In an ideal world this works well and there should never be an issue, but things can go wrong and the primary cause of locomotives rocketing off down the track is short-circuits.  These are usually caused by derailing trains or when you’re putting rolling stock onto the layout whilst the track power is on.  Especially steam engines with lots of wheels!

So why does a short-circuit cause an issue?  When a DCC command station detects a short it turns the power off.  Some will keep trying to turn it back on or will require you to do it manually.  Situations where you have several quick short circuits, for example putting on a steam locomotive, can cause the command station to repeatedly start up and sending out its packet information as it turns the power back on.  If the decoder in the locomotive doesn’t receive a full packet it ignores it.  If this happens too many times on start-up it may get confused and think it’s receiving no packets of information and switch itself to DC.  The problem now is that it will bypass its processor and feed the full 10V to 12V DC from the bridge rectifier directly into the motor and the locomotive rockets off.

This situation can also happen if a train runs into a point or turnout which is set against it.  The system shorts, you change the point, the trains moves forward and shorts again as some wheels have derailed, you lift the derailed item, it shorts again but re-rails itself, the power comes on and other locomotives on the layout rocket off on a joy ride.

So what can you do to stop this? My advice would be to turn the DC running option off on all of your decoders.  This does mean they simply won’t work on a DC layout so bear that in mind if you run them on both.

So how do you do this?  If you have a computer connected to your layout or programming track it should be fairly easy.  Each brand of software is different but the principle is the same.  I use Decoder Pro from JMRI for my programming and the very first screen when you start programming a decoder looks like this.

Below the locomotive address options is the switch for turning off the DC operation.  In the advance setting or Comprehensive Programmer the option is in the basic tab and there is often a tab dedicated to just Analog Control.

But what if you don’t have a computer connected to your programming track?  The option to turn the DC on and off is contained within the CV (Configuration Variable) settings: CV no 29 controls this.  But it also controls the locomotive direction, the speed step settings, Railcom Settings, Speed Curve Settings, long address option and sometimes more, depending on the decoder.  So to work out what number to set CV29 to there are several calculators available on-line to work it out.  This page on Digitax’s website has several CV calculators and the second one down is for CV29.

If you are programing this CV change on an existing locomotive in your collection, rather than a brand new install, it’s a good idea to read CV29 first and see what the value is.  Then replicate this value in the calculator before making the change.  That way you won’t be changing something you don’t want to.

The 2mm Scale Association also has a good calculator here.

Some of the more expensive decoders are smart enough not to suffer from this but I tend to always turn DC off on them all, just to be safe.  Plus if you intend to install any Stay Alive systems to your locomotives you will need to turn it off anyway as a Stay Alive delivers DC power only and it could confuse the decoder again.

With all your locomotives set this way you should have a rocket free layout!

Adding Real Coal Loads To Hoppers

Happy New Year!

2018 is here and after a little time off over the Christmas holiday I’m ready to get stuck back into modeling, 3D printing and generally anything train-related.  And what better way than a blog post about something I’ve been working on that you can also do.

Over the years I’ve collected many different coal cars and the only thing I don’t like about them is the identical plastic coal loads.  So this week’s post is a ‘how to’ for adding real coal loads to hopper cars.

Of course modern block coal trains do have very similar loads in the cars because they are all filled from the same place at controlled intervals and look something like this. (Photo taken by Lewis Bogaty, see his blog here)

But depending on where the load comes from will depend on the size of coal pieces as shown in the image below. (Photo from Virginia Tech Imagebase).

The shape of the load is also effected by the type of coal chute and the operator.  For me I like my coal loads to look something like the cars below; with a twin mound and a random unevenness.  These are Lionel O scale cars, and if you look closely you can see the coal loads are identical!

So what do I do?  Firstly I pick a coal to use; I’ve been using Woodland Scenics’ Mine Run coal, it’s not actually coal but looks just like it and it weighs next to nothing.

Unless the car has a load which is the right shape and set low in the car (I’ll explain what to do with those later) I remove the original load.

This would also be the best time to add any weathering to the car so it doesn’t get onto the coal load. But for this particular car I haven’t done that as it already has a grubby look.

Next I cut a piece of rectangular card which is the same size as the top the car.  It doesn’t have to be an exact fit but it wants to be snug.

The card wants to be set down from the top rim.  This has two functions, it gives me a level to work from and saves me filling the whole car with coal.

To hold it in place I use a splash of super glue on each end.  Any glue will do but I like to do this fairly quickly and superglue sets very fast.  In my previous posts you may have seen me use the Gel superglue which I normally prefer as it doesn’t run.  But today I want it to run into the gap so I’m using the regular stuff.

Next I cut a second strip of card which is thinner than the original, about half as wide.

The second strip is then cut into two pieces.  These will form the mounds, and if you want three mounds simply make them shorter and add a third.

Using my craft knife I cut the mounds at forty-five degrees to make a chamfer.

I repeat this on all four sides.  It doesn’t have to be perfect as it’s going to be covered with coal!

I then put some super glue where the mounds will be.

And place the mounds, trying to get them centered in the car.

Next I use a white glue, simply placed in the car as below.  Woodland Scenics’ Scenic Cement will work or any white glue but I like to use Tacky Glue, simply because it sets quickly and speeds up the operation.

Using and old brush I spread it all over the card trying not to get any on the top edge of the car.

Then the fun bit, simply pour the coal on top.  I recommend doing this on a piece of paper so the excess coal can be picked up and reused.

After about 5 minutes, if you are using Tacky Glue, turn the car over and all the excess coal will fall off.

Pick off any bits that have stuck to the top edge before they set permanently.

If, like me, you want the mounds to be a bit higher simply add a bit  more glue to the top of the mounds.  Also if there’s a hole or gap add some glue there as well.

Then re-cover the car with coal.

After another 5 minutes tip over again to remove the excess and you should be left with a natural-looking load of coal.

I then leave the car overnight just to make sure all the glue sets.  And the car is now ready for the railroad.

Earlier in the post I spoke about cars which have a plastic load which is the right shape and set low in the car.  When the load is set low there is room on top for extra coal without it looking over full. These are easy to do, simply cover the plastic load with white glue, again avoiding the top edge, and pour on the coal.  Even though the plastic loads will be the same shape the poured on coal will take a slightly different pattern each time.

And that’s it for the first post of 2018, I will be back next week with more. In the meantime I’d just like to wish you a great New Year and I look forward to sharing more of my train projects with you.

Lubricating, Oiling and Greasing Locomotives

As well as 3D printing model trains and building model railroads, I do a lot of repairs to locomotives for fellow modelers. These range from simple wire repairs up to total motor and chassis rebuilds or replacements.  One of the issues I come across is over lubricated locomotives, so in this post I will tell you a bit about why this is a problem, and how it should be done.

Some people have said that liberally lubricating moving parts will help preserve them if they are going to be stored for a long time and I can assure you this is not the case.

Over lubricating a locomotive can have the following progressively worsening effects:

It can cause the locomotive to lay a film of lubricant on the rails making the locomotive and others loose traction.

It can make it slippery to handle and possible damage the paint work.

It can make it easy for the mechanism to retain dirt and fluff, which will start to cause binding and over strain the motor.

Oil inside the motor, or on the commutator, can disrupted the flow of electricity to the motor making it run slow or roughly. (What is a commutator? see the image below).

Oil inside the motor on the armature can connect parts of the motor to the power or chassis causing arcing and bad running though intermittent shorting. (What is the armature? see the image below).

And the biggest problem, oil coating the commutator and brushes which will cause a dead short.  This will in turn cause the motor to overheat and burn out; this is when the small gaps between the commutator plates blend into one, so the electricity just passes straight through.

I often get locomotives to repair where there has been smoke coming from the motor or a glow and buzz, rather than turning.  This is normally a sign that the motor has become jammed or the commutator is shorting.  The glow is lubricant and carbon, from the brushes, stuck between the commutator plates acting like a bar fire element.  The smoke is usually the excess oil burning off from the heat being produced. If the commutator or brushes are heavily lubricated electricity simply doesn’t go where its supposed to.  Sometimes if a motor gets to this stage it can get deformed from the heat and will never run as well as is should again.

One other issue I sometimes see is if the wrong type of lubricant has been used.  Some are not plastic friendly and can cause gears and parts to break down.

So what should you do?  The simple answer is ‘just a few drops will do, don’t over lube’ and this is the phrase on the package of the main lubricant I use from LaBelle.

Being an N Scaler I tend to use lubricants from LaBelle as they have a set designed specifically for N scale which are plastic friendly and very fine, but the principles are the same for all scales.

The three products in the kit are oil, gear lubricant and grease.

LaBelle 108 is a very fine oil with a high viscosity.  It is used, sparingly, for moving metal components like valve gear and side rods on steam engines.  It can also be very sparingly used on motor bearings and brush slides etc. but try not to get any on the actual brushes or commutator. (LaBelle 107 is designed more of larger scales such as HO and O).

LaBelle 102 is heavier than the oil but not as thick as grease and is designed for exposed gear boxes.  It contains PTFE (Polytetrafluoroethylene) which has been called “the slickest substance known to man” and is the parent chemical of “Teflon” which is a registered trademark of Dupont Chemicals.  It’s great for metal gears and axles.

LaBelle 106 is a grease, which also contains PTFE.  Their slogan is ‘just a dab’, and they are right.  It’s designed for plastic gear boxes and worm gears.  A dab on one of the gears will work its way through the box and onto any worm gear.  Again, a dab is all you need, over lubricating with grease could start to bind the gear box.

There are lots of companies making similar products, and any good model shop should be able to guide you to the right one for your model.

But which ever you decide to use, remember just a drop is enough.

Fitting DCC to Wrenn OO Locomotives – Vertical Motors

Last week’s post was all about converting Wrenn OO locomotives with horizontal motors to DCC; you can find the post here.  This week I’m going to share with you how to convert the vertical motors.

The vertical motors were used in the City & Duchess 4-6-2s, A4 4-6-2s, 0-6-2 tank engines, Royal Scott 4-6-0s and Bullied Pacific 4-6-2s.  The two engines I’m converting are the ‘City of Birmingham’ and ‘Sir Nigel Gresley’.

To remove the all-metal shell simply remove the screw located at the front and it will come away from the chassis.

As with the horizontal motored locomotives the wiring is very simple.  The black wire goes to the right side pickups and connects to the isolated motor brush at the front of the motor.  The brown disc is the capacitor which acts as a suppressor to prevent interference with televisions etc.  The other wire from the capacitor connects to the chassis and the left side pickup.

All the wires are removed except the black feed from the right side pickup.  The brush at the rear of the motor is not isolated from the chassis and, as with the horizontal motor, it’s this one which gives us a problem.

The steel cap covering the brush simply pulls out to reveal a spring and a brush as below.

The cap fits into a brass sleeve which guides the brush and spring to the armature.  In order to isolate the brush from the chassis this sleeve will have to be removed and replaced.

It’s very unlikely the sleeve will push out; you may be lucky but chances are it will need to be drilled.  Before you do this the armature will need to be removed to prevent damage and metal filings getting where you don’t want them.  In the picture above you can see I’ve removed the magnet and side plates: this is done by removing the main bolt through the motor.  The front brush should also be removed by pulling the end cap out.  Then the top nut above the armature can be loosened and unscrewed.  Note there is a small ball bearing in the cap. The grease should hold it there but be prepared for it to fall out. Then the armature can be removed, normally from the right hand side.  There’s also a small ball bearing in the fitting at the bottom of the armature. Again, it should stay in place but be ready just in case.  The chassis should then look like this.

Using a 5mm drill the old sleeve can be drilled out and the hole made ready for the new 3D printed sleeve; you can see the new sleeve in the bottom right of the image above.  Once the hole has been drilled, clean and remove any burrs from the hole and remove any metal fillings from the chassis.  Before you fit the new sleeve make sure the brush fits through without any resistance.  It should be able to fall through if tipped up.  If it sticks there may be some 3D printing residue inside which can be removed with a drill bit or round file.  The new sleeve can now be fitted and, if necessary, held in place with a little glue.

Then simply reassemble the motor.  Before you put the armature back in check to make sure the ball bearing is still there.  The top nut should be screwed down so the armature spins freely but has no vertical movement; only then should the nut be tightened.  With the brushes refitted, a continuity test should be done with a volt meter to double-check that both brushes are isolated from the chassis.  Then the wires can be added for your DCC decoder.  The red goes to the black wire, the black goes to the chassis, the orange goes to the front motor brush and the gray goes to the rear as below.

Once a DCC test has been performed the shell can be refitted and the loco is good to go.

So where can you get these 3D printed isolating brush holders? They’re available here:

Two Wrenn horizontal motor isolating sleeves.

Four Wrenn horizontal motor isolating sleeves.

Two Wrenn Vertical motor isolating sleeves.

Four Wrenn Vertical motor isolating sleeves.

Two Wrenn Vertical & two horizontal motor isolating sleeves.

I will also keep a few in stock so please drop me an email or message me through the contact page.  If you have a different locomotive which needs a special part to isolate the motor for a DCC conversion I’d be happy to look into it for you.

Fitting DCC to Wrenn OO Locomotives – Horizontal Motors

This week I’m going to share with you a simple way to add DCC (Digital Command Control) to older Wrenn OO locomotives.

Wrenn locomotives date back to the 1960s but don’t be fooled by their age.  They’re very good models and are still widely collected and run.  If you find one in its original box it may even be worth a lot of money, depending on the model inside.

One of their main advantages is they’re all metal, making them very heavy.  This gives them a lot of tractive effort compared to models produced in later years.  The mechanisms are simple but well-built which means most of them are probably still running well.  However these were all designed well before the concept of DCC came along so the motor wasn’t isolated from the chassis.  In fact one of the motor brushes is connected directly to the chassis which makes converting these to DCC a problem.

But to overcome that problem I’ve come up with a simple way to easily make the conversion.  The Wrenn locomotives I’ve come across have one of two types of motor; horizontal and vertical.  This week I’ll cover the horizontal motor which is in the 8F 2-8-0 as pictured bellow, the Castle 4-6-0 and the Rebuilt West Country 4-6-2 which is the locomotive I shall be working on today.

The Rebuilt West Country has the motor and all the wires located under the shell.

With the shell removed you can see a single black wire, which runs from the right hand wheels, connecting into the green wire and going to the right motor terminal.

The left terminal is connected to the chassis by a metal bolt.  Both terminals are linked by a capacitor which acts as a suppressor to prevent interference with televisions etc.  Each terminal also has a spring which keeps pressure on the motor brushes inside the brush holders.

The brush holder on the right is isolated from the chassis and is only connected to the green wire.  The brush holder on the left is the one which gives us the problem.  In the image below I’ve released the spring and the brush has fallen out.  Be carefull not to drop the brush as they are made from carbon, just like a pencil lead, and can easily crack.

The brush holder is made from brass and is fixed directly into the chassis, making a perfect electrical connection.  The brush holder should pull out with a pair of pliers as I have done below.  If not, it will need to be drilled out; if you have to do this dismantle the whole motor first, because you don’t want to damage the inside or get metal filings in the armature.

With the brush holder removed it’s a simple matter of replacing it with something which works as an insulator.  And the answer is a 3D printed brush holder.

These have been designed to be a direct replacement.  They are 3D printed in Shapeways’ Frosted Ultra Detail material and should fit into the hole with a push.  It’s important to check first that the brush slides freely inside the holder.  Any print residue inside may cause the brush to stick and this will prevent the locomotive from running.  Any residue can be removed with a drill, the same size as the brush, or a round file.  If the brush holder is a loose fit in the hole simply fix it in place with some superglue.  (Superglue is made from acrylic and so is the Shapeways FUD)

The black wire from the right hand side wheels has been cut and will be joined to the DCC decoder.  The capacitor has also been removed.  Under the left motor terminal is a bolt which also connects this side back to the chassis; this needs to be removed and left out.

At this stage a continuity test using a volt meter is a good idea to ensure the two terminals really are isolated from the chassis and both left and right wheels.  If they are, then the brush can be re-fitted and the spring clipped on to hold it in place.  The wires from the DCC decoder can now be soldered to the motor terminals.

The power feeds can now be connected; one goes to the black wire and the other to the chassis.  I connected the chassis wire to the screw holding on the weight at the front of the loco.

And that’s it, the loco is chipped and ready for testing.

Next week I’ll share with you how to isolate a vertical Wrenn motor and where to get the 3D printed brush mounts from.